The gun attack happened at about 18:50 local time on Saturday at Blakestown Cottages in Blanchardstown.
Irish national broadcaster RTÉ reported that the victim had been shot in the head.
It said gardaí (Irish police) are treating
the case as a gangland murder.
The scene has been sealed off for a forensic examination.
The Garda Síochána (Irish police force) said that a car that was found burnt out in Clonee in County Meath could be connected to the attack.